An injury in which the ends of the bones that form the shoulder joint are forced from their normal positions. A dislocated shoulder is usually caused by a blow, a fall, or other trauma. An injured shoulder that is visibly out of position, misshapen, swollen, difficult to move, and intensely painful probably has been dislocated or broken. Numbness can indicate nerve damage. Medical attention should be sought immediately. A dislocated shoulder is diagnosed by physical examination and X ray and treated by a procedure called reduction, followed by at least 2 weeks of arm immobilization in a sling.